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Author Topic: BSD micro R/C "peanut" scale Sterling Mambo  (Read 2416 times)
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Hank G B Z
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« on: March 17, 2014, 11:28:25 AM »

Hey Everybody,

  Well there is not deadicated "micro" section here so i thought i'd just start this over here in Electrics.  Bob Selman (BSDmicrorc.com) has come out with a line of "peanut" scale (13" ws) kits of vintage R/C planes.  There is the Mite, the Mamabo, Esquire, and some others i don't recgonize.  I order up the Mambo and the gear box that goes with it and here is a bit of a build thread. 

  The plane uses a mini vapor brick and a J-3 cub motor in Bobs own gear box design.  The J-3 cub motor is similar to the ember or big vapor motors but has a different KV.  IT's 6mm in dia and i haven't measured the length yet. 

  I got my kit on Saturday and started it on Sunday.  Here is where i am after a few hours of building.  The wing panels are assembled, and the fuse is assembled.  I need to make some corrections to the fuse so the elevator is plum to the verticle datum.  Also i over shaped one trailing edge piece so now i had to add some wood and reshape it. 

  It's a fun build, really old school style.  The wing is built hell for stout and i'm sure one could save few grams there if they wanted to redesign the wing. I'm not going to do that now because i like building this model so much, it's nice knowing that the wing is so stiff that it won't warp when the tissue is shrunk. 

enjoy the pics

Hank
Attached files Thumbnail(s):
BSD micro R/C "peanut" scale Sterling Mambo
BSD micro R/C "peanut" scale Sterling Mambo
BSD micro R/C "peanut" scale Sterling Mambo
BSD micro R/C "peanut" scale Sterling Mambo
BSD micro R/C "peanut" scale Sterling Mambo
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Konrad
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« Reply #1 on: March 17, 2014, 11:40:12 AM »

Wow, there is a lot more balsa than I would have expected, both in the wing and fuse. So, this makes me want to see the power system.
Also you have got to stop showing other planes in the photos! Roll Eyes Now I want to know about the fuse that is acting like a tub with some plastic parts thrown in. Also I see a wing that looks like part of an SE5(a).

All the best,
Konrad
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Hank G B Z
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« Reply #2 on: March 17, 2014, 12:02:19 PM »

Konrad,

  Yeah i'm a little suprised by the wood in the wing too.  If i feel it flies too fast i'll build a lighter wing.  I'll get some better pictures of the gear box and stuff when i get it assembled. 

  The "Tub" is a portly Guillows Chipmunk that's slowly being worked on.  and the wing is to my Stevens aero Se5.  It's down for some maintence due to me dropping it at the field and failing to pick up all the parts. 

Hank
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« Reply #3 on: March 17, 2014, 12:09:34 PM »

Hey Everybody,

  Well there is not deadicated "micro" section here so............


If you keep this up, and I hope you do, we're probably gonna need one.
This is cool.


Also you have got to stop showing other planes in the photos! Roll Eyes

I get a kick out of that. All kinds of side note stuff going on in some of these posted pics...
Mike Stuart (I think it was Mike) had a Pnut and some glue sitting on the table for his Jumbo pics a couple of weeks ago that had me wondering...watwazthatthere?

Tony
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Hank G B Z
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« Reply #4 on: March 20, 2014, 11:57:42 AM »

Tony,

  It's good to have you along.  I don't know if there needs to be a "micro" section or not.  Most of my micros can go in "stick and Tissue r/c" section.  In fact this one could probably go there since i plan on covering with tissue. 

  anyway, i got some more work done.  I have joined the wing panels.  The plans call for 3/4 dihedral under each wing my building board happens to be 3/4 of an inch thick so i just arranged it so the root of the wing was in line with the edge of the bench and then sanded away.  The two wing panels are just but jointed together.  I think i'll glue a band of tissue around the center like one would with Fiberglass on an old model.  I also bent up the landing gear.  It's a top hat style or v style anyway my gripe is that the wire in the kit is my smaller than the pocket so either i fill the pocket it, make new landing gear out of thicker wire or do the right thing and make some torsion style gear.  I'm not sure what i'll do yet. 

  I have a technical question about this model.  It only has elevator on one side and i'm ok with this i've flow old times like this and there is no performance lost that i can detect.  I'm a little concerned about not having any positive incidence in the tail plane.  My thought at the moment is to leave the horizontal stab at zero degrees and then make the elevator the whole span of the stab so that I can add "down" trim to get the benefit of positive incidence.  My question is if I don't make the elevator the whole span and add some down trim my suspicion is that i'll get some very adverse trim effects especially with speed.  Am i correct in thinking this? 

Anyway, enjoy the pics,

Hank
Attached files Thumbnail(s):
Re: BSD micro R/C "peanut" scale Sterling Mambo
Re: BSD micro R/C "peanut" scale Sterling Mambo
Re: BSD micro R/C "peanut" scale Sterling Mambo
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Konrad
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« Reply #5 on: March 20, 2014, 01:55:00 PM »

The Mambo was designed as a single channel ship. As such she was always climbing under power. We needed to make turns to keep her out of a stall. To do a loop we would spin her down then release the rudder. With the built up speed she would loop when the wings returned to level. Now we had to make an S turn right after the loop to kill the speed if we didn't want a climb to stall.

I had her trimmed for a slow gentle hands off, engine dead, glide.

As to trim with your micro I'd leave her as BSD designed her (maybe ask the OEM for his input as to why she is the way she is). But yes, any asymmetry in trim will become more pronounced as she gains speed. You might get a bit of roll as she gets going fast.

All the best,
Konrad
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« Reply #6 on: March 20, 2014, 04:29:23 PM »

I doubt if there will be much problem with the one-sided elevator nor do I think there will be too much "speed" to worry about.  I've flown a few one-sided oldie conversions (wet powered) and there were NO control issues.  If weight is too high (always is), you can "add lightness" by putting a few holes in the rear fuz and tail surfaces.  The stout wing will prove itself in the first cartwheel.  There should be enought incidence in the wing seat (only needs about 1.5-2°) and is easily shimmed.

You also have to take into consideration the low thrust of the brick servos moving a solid wood surface.  The Mambo that I had back in the Dark Age (Fox .15X powered), first flew with a simple Citizen Ship single function escapement (rubber band jobbie) and had only 3/16th" throw - each way.  It was a handfull if the button was held too long (over one second).  The plane was a great flyer once I learned not to overcontrol and turned into a GREAT flyer with the upgrade to a compound escapement with '"kick-up" elevator.
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Hank G B Z
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« Reply #7 on: March 21, 2014, 11:05:18 AM »

Thanks for the response guys. 

  I think the asymmetrical elevator is just to make building easier.  My thoughts on positive incidence in the tail come from the fact that I hate having my models flying tail low (not on step) on slow fly by.  Pit is right in that changing the incidence on the main wing is easy since this model will have a rubber banded on wing.  As for saving weight.  THe fuse and tail feathers are 1/20th sheet and nice light wood.  Any weight saving there will just weaken the structure or make the model more prone to hangar rash.  The place to save weight is in the wing.  I have not weighed it yet but i know that one could save at least 2 grams there.  Anyway, I'll build the tail stock and if i have issues with not being on step i'll just make the elevator symmetrical and move on with life. 

Hank 
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Hank G B Z
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« Reply #8 on: March 26, 2014, 11:04:31 AM »

Well I didn't get to much done on the mambo this weekend.  I did get the actual J-3 cub motor that the gear box calls for.  My LHS had a few in stock so I grabbed one.  My other motors were vapor motors.  I think Bob should try and find a source for these motors other than horrizon, would make selling these kits easier.  I'm currently trying to figure out a good way to get the pinion off the motor.  My gear puller isn't small enough to push the pinion off the 6mm motor.  I'm investigating making a needle to fit into my puller or seeing if i can rig something up in a drill press. I'll keep you guys posted. 

Since Konrad asked about it here is a picture of my fixed Stevens aero Se5. 

Hank
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Re: BSD micro R/C "peanut" scale Sterling Mambo
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Konrad
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« Reply #9 on: March 26, 2014, 11:14:45 AM »

Nice effect on the GWS prop.
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Hank G B Z
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« Reply #10 on: March 26, 2014, 11:25:59 AM »

Thanks Konrad,

  Actually the most useful thing old "hippie" rob out at Rosevelt told me was that Markers work great for making orange GWS props look, well, not like an orange GWS prop.

Hank
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Konrad
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« Reply #11 on: March 26, 2014, 11:40:28 AM »

Thanks
I need to see what is going on with the old gang at Roosevelt. I'd forgotten about that place of mayhem.
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« Reply #12 on: March 26, 2014, 11:44:51 AM »

All the old gang is still there.  My advice is to go early before the guys start to take part in their other "recreational" activities. 

Hank
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« Reply #13 on: March 26, 2014, 11:56:20 AM »

You mean the place has gone to pot?
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« Reply #14 on: March 26, 2014, 12:00:14 PM »

Pot, Rockets, birds, Large Helicopters, lasers, crazy planes with lights on them, beer, and who knows what all. 
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Hank G B Z
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« Reply #15 on: March 27, 2014, 11:19:28 AM »

Well I got some more work done on the mambo.  i'm now ready to cover.  I built the gear box last night.  After all my fretting for the pinion puller turned out that the easiest thing to do was to smash the pinion in a vice and it came out of round and slid off the shaft.  I ran the motor with the tri turbo prop and it seems to have pleanty of pull.  I'll charge the battery up tomorrow and run it with the watt meter and get some real power readings.  I put a plug on the leads from the brick so i can plug and unplug the motor.  I got the female plug from a dead vapor brick and the male plug was already on the motor.  I should have shortened the wires some but i don't want to mess with it because the small wire is kinda difficult to solder with my iron.  I put the last few pieces of wood on the front of the fuse now that the motor is installed and working.  Then I put everything on the scale, right now i'm at 20 grams.  Most of that is equipment.  The wing weights 4 grams so it's not as heavy as i thought.  The prototype came in at 22 grams i don't know if i'll make that but i should be close.  Hope to get her covered and finished up this weekend.  Stay tuned.

Hank
Attached files Thumbnail(s):
Re: BSD micro R/C "peanut" scale Sterling Mambo
Re: BSD micro R/C "peanut" scale Sterling Mambo
Re: BSD micro R/C "peanut" scale Sterling Mambo
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Hank G B Z
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« Reply #16 on: March 28, 2014, 10:39:09 AM »

Well Power tests are in.  And with a 70mah battery fully charged the motor and prop combo pulls .8 amps making about 3 watts of power.  It wants to pull the fuse with the equipment in it out of my hand so I think it's a winner.  Though I cant help but think that the vapor motor is probably a lower KV and putting that in this gear box with a GWS 3x2 prop might also be a good combo.  Only problem there is that the GWS prop has a bigger hole in the middle which would require drilling spur gear and opening the holes in the gear box frame to accept the larger diameter wire.  More possibilities. 

Hank
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Konrad
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« Reply #17 on: March 28, 2014, 10:50:35 AM »

Gear driven 3x2 props, now that is paradigm shift in my way of thinking. Can one get enough pitch speed with these small props?

What is the stock BSD prop for this system.
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« Reply #18 on: March 28, 2014, 11:22:03 AM »

Konrad,

  The stock prop is called the Plantraco "tri turbo" prop.  It appears to be a pusher prop.  I don't know the specs but from looking at it by eye it's less diameter and less pitch than the GWS 3x2 prop. 

  The micro guys really like the tri turbo prop.  And in my current set up i know it will work fine on the mambo.  My thinking is along the lines that If i ran an R/C web store and developed a gear box i'd work to have it work with as wide a motor and prop combination as I could come up with.  But hey that's me and I don't run an r/c web store for a reason. 

Hank
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« Reply #19 on: March 28, 2014, 01:14:11 PM »

Gear driven 3x2 props, now that is paradigm shift in my way of thinking. Can one get enough pitch speed with these small props?

What is the stock BSD prop for this system.
Look at the gears!  That can't be much more than 2.5:1 reduction.  Given the generally high KV of pager motors, there will be plenty of RPM's to make it work just fine, and the little buggars make the tiny, but relatively weighty, PZ scalers really zip.

'Course, the proof of the pudding is in the eating...
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« Reply #20 on: March 28, 2014, 01:22:19 PM »

Konrad,

  The stock prop is called the Plantraco "tri turbo" prop.  It appears to be a pusher prop.  I don't know the specs but from looking at it by eye it's less diameter and less pitch than the GWS 3x2 prop. 

  The micro guys really like the tri turbo prop.  And in my current set up i know it will work fine on the mambo.  My thinking is along the lines that If i ran an R/C web store and developed a gear box i'd work to have it work with as wide a motor and prop combination as I could come up with.  But hey that's me and I don't run an r/c web store for a reason. 

Hank
I'm wondering if the Tri Turbo prop would help the performance of my Dumas Hawk direct drive? While the GWS 3x3 is working fine I find I'd like a bit more vertical performance..
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« Reply #21 on: March 28, 2014, 01:56:13 PM »

Pit, Konrad,

  The tri turob fan prop is about 65 mm in diameter and no pitch given on the plantraco website. Apparently it's from driving a helicopter tail rotor in direct drive.  Anyway.  I don't think this prop is any better than a GWS prop it's just available. 

   Konrad, In regards to your hawk.  If you're using the 5 gamm motor like me then just go to the GWS 4.5x3 prop for more load and vertical.  I use the GWS rubber bushings and some heat shrink to hold the prop on and it has never come off. 

Hank
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« Reply #22 on: March 28, 2014, 02:49:55 PM »

Pit, Konrad,

  The tri turob fan prop is about 65 mm in diameter and no pitch given on the plantraco website. Apparently it's from driving a helicopter tail rotor in direct drive.  Anyway.  I don't think this prop is any better than a GWS prop it's just available. 

   Konrad, In regards to your hawk.  If you're using the 5 gamm motor like me then just go to the GWS 4.5x3 prop for more load and vertical.  I use the GWS rubber bushings and some heat shrink to hold the prop on and it has never come off. 

Hank
Yep, it is the 5 gram motor. But on 2 cells and the GWS 3x3 I'm puffing batteries as it is. I know the new 45C cells are out. I need to try them. Are you using 2 cells with your 5g motor and GWS 4.5x3?
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« Reply #23 on: March 28, 2014, 03:16:47 PM »

The Triturbofan prop in my flight tests and in static tests has been better than all 2.5-in GWS or U-80 props that I have tried. It can be tractor or pusher, but you must put it on the shaft so that the convex side is forward and you may have to change your wiring connections. I think that it was originally a RC blimp prop before small helicopters were common. Some props that look identical to the Plantraco Triturbofan prop were labeled Snap and Fly the last time that I bought any.

Yes, I flew a capacitor FF plane today using a Triturbofan prop, a 10-g AUW plane, and a 7-mm "Pager" brushed motor direct drive. This motor was the ~2-ohm hottest version (rosy end cap) from BSD Micro RC.

Have fun.

Fred Rash
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« Reply #24 on: March 28, 2014, 04:10:59 PM »

Fred,

  Thanks for the advice on the tri tubro fan prop.  I have the convex side out. 

Konrad,

  I use 2 cell either 180 or 200 mah batteries in my Hawk.  Haven't killed any yet and I haven't killed the motor. 

Hank
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